The objective of this proposal is to investigate mechanisms of mini spindle (msps) gene function in Drosophila, as a means of understanding cytoplasmic organization and its role in gametogenesis. Mini spindles was originally identified as a microtubule binding protein, and is a required component of mitotic and meiotic spindles in a variety of organisms, including Drosophila, Xenopus, and humans. The human homolog, ch-TOG, is overexpressed in certain cancer cells, highlighting the importance of this protein family for normal cellular functioning. Recent research has indicated a role for mini spindles in bicoid RNA localization during Drosophila oogenesis, raising the possibility that mini spindles participates in multiple microtubule-based events throughout the life cycle of a cell. In order to advance our understanding of mini spindles function, we will: (1) Examine the involvement of msps in a variety of microtubule-based events during oogenesis, (2) Test requirements for msps function during oogenesis, and (3) Identify potential partners for msps via genetic interactions. These studies are designed to answer some basic questions regarding msps function in non-dividing cells, since virtually all research to date has focused on the role of msps in spindle function. For example, does msps influence the structure of cytoplasmic microtubule networks? Does msps act in concert with other microtubule-binding proteins? Is msps a general, or a specific, regulator of microtubule function? As an integrated whole, these experiments will provide valuable information on the extent of msps function in oogenesis and will begin to address mechanistic questions as well. This research is of particular interest because it is becoming clear that many characteristics of cytoskeletal function are highly conserved, and the subcellular regulation of microtubule structure is likely to be essential to the functioning of all cells. [unreadable] [unreadable]